Laminate components may be formed by arranging a stack of ply layers on a mould tool, allowing the stack of plies to deform to the shape of the tool and then curing the plies to produce a solid consolidated component. When a laminate stack is folded over a complex three-dimensional moulding surface of the tool, some of the ply layers may be forced to contract or expand depending on the nature of the surface curvature. If the ply layers comprise a material which has minimal ability to contract, for example carbon fibre or Kevlar or glass fibre in a composite material, the geometry may cause wrinkling in the ply layers of the finished laminate component.
Wrinkles in the plies of composite laminate components are undesirable because wrinkles may lead to voids, discontinuities and resin rich or resin poor regions in the component. These defects may result in reduced performance of the component, for example reduced strength and stiffness, and may affect the durability of the component. A composite component having wrinkle in its ply layers may, therefore, perform less well than the intended component according to the design shape of the component without wrinkle.
The development of wrinkle, especially wrinkle affecting external plies of the laminate stack, may also lead to reduced accuracy of surfaces of the component, presenting a particular problem if wrinkle develops on a surface which is designed to engage with other components, and may require concessionary work to be carried out before the finished component can be accepted.
Wrinkle may develop in an unpredictable manner such that, when multiple composite components are formed using the same or similar tools, the components may exhibit different wrinkle characteristics. For example, the extent of wrinkle and the location or locations at which wrinkle develops in each component may vary. This unpredictable nature of wrinkle development leads to non-standard (and therefore time consuming) inspection, correction and justification work, and makes it difficult to produce substantially identical components having predictable features and properties.
For these reasons, it is generally desirable to eliminate or control the development of wrinkle within the laminate stack during the moulding process, so that the shape and properties of the component produced may be optimised and so that multiple components produced to the same design can be made substantially identical.